1. Field of the Invention
The present invention relates to techniques for security monitoring, and more particularly to video monitoring system with video signal encrypted and the method for doing the same.
2. Description of Related Art
With further development of multimedia technologies, video monitoring systems are widely used in all kinds of areas such as security operations and public security managements. Commonly, a video monitoring system comprises a plurality of monitoring cameras each of which is provided for capturing video data representing a predetermined monitoring area and a monitoring terminal on which the video data can be displayed for supervisors.
FIG. 1 is a schematic block diagram showing a conventional monitoring camera. As shown FIG. 1, the monitoring camera comprises a lens 111, an image sensor 112, an image signal process 113, an image buffer 114, a video encoder 115 and a digital-to-analog (D/A) converter 116.
The lens 111 focuses lights from a scene onto the image sensor 112. The image sensor 112 generates digital image data by converting the light signal from the scene to the analog electronic image signal representing the scene and further converting the analog electronic image signal to the digital image data. The image signal processor 113 adjusts quality of the digital image data received from the image sensor 111, such as auto explosion adjustment, auto white balance adjustment, lightness adjustment or color adjustment. The image buffer 114 may buffer one line of the digital image data or one frame of the digital image data from the image signal processor 113. The video encoder 115 encodes the digital image data received from the image buffer 114 into the digital video data according to a National Television System Committee (NTSC) pattern or a Phase Alternate Line (PAL) pattern and outputs the encoded digital video data to the D/A converter 116. The D/A converter 116 converts the digital video data to the analog video signal and transmits the analog video signal to the monitoring terminal of the monitoring system. As a modification of the monitoring camera, the image signal processor 113 and the image buffer 114 may not be included.
The monitoring terminal of the monitoring system receives the analog video signal from the monitoring camera, converts it to the digital video data and displays the digital video data for the supervisors via a video output unit thereof.
However, during transmission of the video signal, especially by wireless ways, the video signal transmitted from the monitoring camera shown in FIG. 1 has not been encrypted, it may be obtained by other unauthorized video receiver such as normal television besides the authorized monitoring terminal, thereby exposing the monitoring video signal to unauthorized uses.
Thus, there is a need for techniques for encrypting the video signal in the monitoring system.